MadGraph5_aMC@NLO

Pythia8 shower failed since it did not accept any event from the MG5aMC event file

Asked by Aria Radick

Hi,

I'm trying to do a matched jet sample with MG 2.6.6 using the Hidden Abelian Higgs Model UFO from http://insti.physics.sunysb.edu/~curtin/hahm_mg.html, but I am getting the following error:

Command "generate_events run_01" interrupted with error:
InvalidCmd : Pythia8 shower failed since it did not accept any event from the MG5aMC event file.

I'm doing the following to generate the process:

import model --modelname HAHM_variableMW_v3_UFO
generate p p > h > hs hs @0
add process p p > h > hs hs j @1
output sm-s_jets
launch
shower=pythia8
set run_card ickkw = 1
set run_card auto_ptj_mjj True
set run_card xqcut 15

This problem seems similar to https://bugs.launchpad.net/mg5amcnlo/+bug/1674341 , but I see that that problem has already been patched out a while ago. The end of the pythia8 log file in split0 follows:

*------- PYTHIA Error and Warning Messages Statistics ----------------------------------------------------------*
2810 | |
2811 | times message |
2812 | |
2813 | 500 Abort from Pythia::next: processLevel failed; giving up |
2814 | 1 Abort from Pythia::next: reached end of Les Houches Events File |
2815 | 2500 Error in ResonanceDecays::next: no open decay channel |
2816 | 2 Info from SLHAinterface::initSLHA: No MODSEL found, keeping internal SUSY switched off |
2817 | 2 Info from SLHAinterface::initSLHA: importing MASS entries |
2818 | 4 Warning in SLHAinterface::initSLHA: ignoring DECAY tables |
2819 | 3 Warning in SLHAinterface::initSLHA: ignoring MASS entries |
2820 | 3 Warning in SLHAinterface::initSLHA: ignoring QNUMBERS |
2821 | 2 Warning in SLHAinterface::initSLHA: ignoring empty DECAY tables |
2822 | 1 Warning in SLHAinterface::initSLHA: using QNUMBERS for id codes < 1000000 may clash with SM. |
2823 | |
2824 *------- End PYTHIA Error and Warning Messages Statistics ------------------------------------------------------*

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Olivier Mattelaer (olivier-mattelaer) said : 		#1

Hi,

Does it work without matching/merging?

My guess here is that pythia author might be able to give you more help on this than me.
However the following line:
2815 | 2500 Error in ResonanceDecays::next: no open decay channel |
seems to indicate that you have issue with some decaying particles.
What is the mass/width of your hs (as well as what is the quantum number of such particles?)
If that particle does have a width, then you need to indicate to Pythia how to decay it. ( via the BR information within the param_card)

Cheers,

Olivier

Revision history for this message
Aria Radick (aradick) said : 		#2

It does work without matching/merging.

The mass of hs is 25 GeV and the width is 5.24 GeV in the param_card, the hs is a scalar and is charged under a dark U(1) but a singlet in everything else, and mixes with the SM Higgs via an |H|^2 S^2 operator. Is the BR information different than the total width listed in the param_card?

Thank you,

Aria

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#3

Hi,

Why not using the (safer) syntax:
generate p p > h, h > hs hs @0
add process p p > h j , h > hs hs @1

What is the mass of the "h"? is it 125GeV?
What is the value that you choose for the merging scale?
I would suggest to look at this paper: arXiv:1507.00020
Where i did a similar process and where the setup for the matching/merging is detailled (it is not trivial to have it right for this process)

Cheers,

Olivier

Revision history for this message
Aria Radick (aradick) said : 		#4

I still get the same error with that syntax.

"h" has mass = 125 GeV
By merging scale, do you mean xqcut? I have tried many different values from 1 to 30 GeV but they all have continued to give the error.
Which section of that paper, the g g > h? I attempted to see if that process would work (with this particular model loaded) and it seems to work out. It seems that pythia doesn't like the h > hs hs portion.

Thank you for your help,

Aria

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